Hi, I am a newbie here. I enjoy travel, but don't do it as often as most people here (I suspect).

Anyways, a generous family member is footing the bill on a family vacation to Barcelona. I am tasked with booking all the trips... and that means I get all the miles!

So... 7 adults and 1 child, roundtrips from BWI/DCA/IAD to BCN. Economy. Outbound in late March, returning mid April. 2 adult tickets have already been booked on United Airlines (chosen for schedule, it is historically my least favorite Legacy carrier)... 6 tickets to go. All tickets will be booked on AMEX Platinum, and I have about 80 AMEX points as well.

My goal is to pool the miles from everyone's transatlantic flights, then use them for free (or nearly free) international travel. My dream is South America next year... But if I don't get enough points, I can just spend them on domestic travel.

What is the best way to collect all these miles? Should I stick with carriers in the same alliance? Any other tips? Should I transfer points immediately, or wait? What quantity of points is too low to bother transferring? What kind of reward should I expect from 8 transatlantic roundtrips? I am new to the miles game.

Thank you kindly.